Japanese Patent Laying-Open No. 2003-292397 (PTD 1) and International Publication No. 2009/099130 (PTD 2) disclose polycrystalline diamond manufactured by directly converting graphite to polycrystalline diamond without addition of a sintering aid, a catalyst and the like.
Japanese Patent Laying-Open No. 9-142933 (PTD 3) and Japanese Patent Laying-Open No. 2005-239472 (PTD 4) disclose polycrystalline diamond including polycrystalline diamond and a component such as metal carbide or metal oxide.